The present invention relates generally to a cutting apparatus such as a circular saw assembly for use on metal.
In a known form of cutting apparatus, the machine comprises a support structure or base and a cutter assembly which for example comprises a pivotal member or arm carrying a cutting tool, which thus operates from below in an upward direction. The support structure is a box-like construction which is more or less closed and which is covered at the top by a cover plate. The pivotal member is mounted in the support structure, underneath the cover plate. When the cutting tool is in the form of a circular saw, for example, the shaft of the saw is mounted on the top side of the pivotal member and the cover plate has a slot therein. The material to be sawn therefore rests on the top of the cover plate and is clamped fixedly in position by suitable clamping means. The material is then sawn by the circular saw projecting through the slot in the cover plate, as the pivotal member or arm is pivoted in an upward direction through the slot.
In other known forms of the above-indicated cutting apparatus, the mountings for the pivotal member or arm are fixed to the underside of the cover plate, whereby it is possible for the cover plate to be arranged rotatably in a horizontal plane, thereby also to permit inclined cutting operations.
However, the known cutting apparatuses suffer from a number of disadvantages, the most serious of which are as follows:
The cover plate on which the material to be sawn is also laid must be of such a size that it adequately covers over the entire support structure therebelow. As however the support structure must accommodate the entire pivotal assembly, including the motor drive for the cutter arrangement and the feed means, the cover plate must be of very large size, in relation to the size of the cutter (for example a saw blade); for reasons of rigidity and strength, the large dimensions of the cover plate in turn mean that the cover plate must be relatively thick.
As the cutter is mounted on the pivotal member which is disposed underneath the cover plate and as the cutting operation is effected in an upward direction through the slot in the cover plate as the cutter is advanced into the material to be sawn through that slot, the thickness of the cover plate means that there is a substantial reduction in the cutting region, relative to the cutting region found in cutting apparatuses which do not have a cover plate. The percentage reduction in the depth of cut of cutting apparatuses having a cover plate can be up to about 30%, in comparison with cutting apparatuses which do not have a cover plate.
Another disadvantage of the above-described constructions is that large openings must be provided in the walls of the box-like support structure, for various reasons. Such openings are required inter alia for the purpose of maintenance of the motor drive, lubricating the saw carriage or slide and the feed means, and also for replacing the saw blade, adjusting the brushes or wipers for the dust and other material produced by the cutting action or the finger-type dust-removal reamers, for adjusting the means for cooling the saw blade, and the like. All those openings weaken the support structure and give rise to a high level of expenditure, particularly when the requirements made in respect of the machining capacity of the apparatus are high, which therefore involves high requirements in regard to rigidity and strength of the cutting apparatus. Added to that is the consideration that, for safety reasons, all the openings must be properly covered over, which once again gives rise to additional cost.
Another disadvantage of the above-described forms of cutting apparatuses is that the large amount of space required for the support structure makes it very difficult for the apparatus to be integrated into an automatic production system.
Therefore, in order for cutting apparatuses of the above-described kind to have adequate dynamic or vibration strength, they involve a high degree of capital investment, with at the same time a substantial reduction in the theoretically possible cutting range. With increasing sizes of cutting apparatuses (saw blades), the expenditure required in relation to the rigidity of the machine increases as the overall strength and stability of the support structure drops rapidly as the dimensions of the support structure increase, and compensation in that respect, by means of additional ribs or by an increase in the thicknesses of the materials used, becomes more and more difficult and expensive.
On the other hand, the line of development in cutting apparatuses which are for example in the form of cold circular saws is in the direction of increasing cutting rates, with saw blades which are tipped or clad with hard metal such as a carbide being used to an increasing extent. However, that line of development requires machines which are more and more rigid and in which the amplitudes of vibration produced must be less than 0.015 mm in the feed direction. The known constructions of the general kind referred to above cannot meet those requirements, or can only meet such requirements by incurring a high level of expenditure, in which respect the capital investment required increases out of all proportion to the increasing diameter of the cutting tool.
Finally, the above-mentioned disadvantages have also had the result that the cutting apparatuses referred to above are in practice only used with cutters or saw blades of relatively small diameters, and in addition are only employed for sawing tubular or shaped or profile material.
On the other hand, the type of cutting apparatuses which have a cutter that operates in an upward direction enjoys substantial advantages, particularly in regard to sawing hollow members such as tubes. For example, such advantages are in particular that, when performing a cutting operation from the underside of the hollow member to be cut, dust and other material produced by the cutting action is drawn into the cut only to a very slight degree. Thus, when using such cutting apparatuses, the cut surfaces produced are substantially smoother than when using for example cutting apparatuses which operate in a downward direction and in which the cut surfaces are seriously damaged or marked due to dust and other material produced by the cutting action being drawn into the cut.